Electronic components are typically mounted on printed circuit boards (PCBs). In order to cool components, such as, for example, processors, integrated circuits, e.g., application specific integrated circuits (ASICs), potentiometers, etc., a heatsink is often mounted proximate to the component. The heatsink typically has a large mass relative to the component it cools. The force necessary to retain this large mass under shock and vibration tends to approach the limit of the load that the component can endure. It is very difficult to hard-mount the heat sink to a PCB without damaging the component. In addition to the force needed to provide the electrical interface between the component and the PCB and the thermal interface between the heatsink and the component, there may also be forces caused by shock and vibration that must be withstood.
Referring to Prior Art FIG. 1, a cantilevered heatsink 110 is shown, having a cantilevered end 195. Heatsink 110 is mounted above a component 115, e.g., a processor, a power pod 140 and a thermal interface 150 and resides within a heatsink frame 120. A retention frame 130 provides a surface for attaching heatsink 110 to a printed circuit board (PCB) 190 with mounting screws 180. Not shown is a socket that serves to provide an electrical interconnect between PCB 190 and processor 115. Processor 115 is mounted to a substrate 170. The socket, substrate 170, processor 115 and thermal interface 150 comprise the stackup upon which heatsink 110 resides.
Each component in the stackup has design tolerances that allow for small variations in thickness (e.g., ±0.4 mm). Depending on the design tolerances of the components within the stackup, the thickness of the stackup may vary by as much as 0.5-2 mm. When heatsink 110 is placed over the stackup, a gap 160 may exist between heatsink 110 and retention frame 130, e.g., due to variances in the thicknesses of components in the stackup. The system is designed to have a gap 160 to ensure that all force is driven through processor 115 uniformly. Heatsink 110 is then secured to retention frame 130 by tightening mounting screws 180. Where gap 160 exists, in order to overcome forces that are applied during vibration (for example, during shipping and handling or during shock or shock testing) by cantilevered end 195, an amount of force may be provided by mounting screws 180, in attempting to close gap 160, that can potentially damage processor 115. The processor 115 might be instantly broken from too much force being applied by mounting screws 180, or a latent failure (small defect) may be introduced that causes breakage after a series of thermal cycles, for example.
One conventional art approach includes using shoulder screws and springs to control the load. However, in instances in which the heatsink is cantilevered away from where the socket is located (e.g., the mass is not centered over the socket), or where the component and/or heatsink is especially heavy, the amount of force needed to hold the component in place can exceed the capability of springs. In such a case, shock or vibration loading may decouple the electrical interface between the processor and the PCB. Additionally, it is very difficult to control the cantilevered mass without driving very non-uniform pressure distributions to the processor.
Another conventional art approach includes the use of wedge-lock hardware at the cantilevered end of the heatsink. This hardware comprises a number of finely machined small pieces that can be expensive and/or difficult to manufacture. In addition, the installation requires aligning a number of small loose components which can render production difficult and time consuming.